1. Field of the Invention
The present invention relates to numerical controller and, in particular, a numerical controller capable of easy settings of table axis operation of a punch press machine.
2. Description of the Related Art
In a punch press machine, to achieve a target hit rate (the number of times of press per minute), a function called “positioning with optimum acceleration” is provided in which speeds, acceleration and deceleration time constants, and position gains of a table axis are switched at seven stages in accordance with the movement amounts on the X axis and the Y axis (table axis). When this function is used, movement amounts as switching boundaries (hereinafter referred to as boundary values), and speeds, acceleration and deceleration time constants, and position gains are set for each of the X axis and the Y axis. In this setting, as depicted in FIG. 9, since many items including boundary values, and speeds, acceleration and deceleration time constants, and position gains have to be set for each of the X axis and the Y axis for seven stages, a problem arises in which setting is difficult and takes a long time.
Meanwhile, as a prior art technique for supporting setting of an acceleration and deceleration time constant for an axis to be controlled, Japanese Patent Application Laid-Open No. 4-335410 discloses a technique, as depicted in FIG. 10, in which an acceleration with the acceleration torque of which is the upper-limit Lmax of motor performance is found from a rapid feed rate F in a block with a movement amount d, feed rate-torque characteristics of a servo motor, and inertia of load; an acceleration and deceleration time constant T is found from the acceleration; and the largest time constant among all drive axes is set as a time constant for each axis.
In the punch press machine, press is adapted to be performed upon completion of the movement of a block. Here, a process failure occurs unless the servo motor is settled. In the technique disclosed in Japanese Patent Application Laid-Open No. 4-335410, the acceleration and deceleration time constant T is found from the acceleration with the acceleration torque of which is the upper-limit Lmax of motor performance. In the case of the punch press machine, when the axis movement is performed with high acceleration or deceleration, as depicted in FIG. 11, a problem may arise in which press timing has to be delayed due to, for example, occurrence of an overshoot when table axis movement is completed and the acceleration or deceleration set in accordance with the technique disclosed in Japanese Patent Application Laid-Open No. 4-335410 may not necessarily have an optimum value. Therefore, the technique disclosed in Japanese Patent Application Laid-Open No. 4-335410 cannot be simply applied to setting of an acceleration and deceleration time constant for the table axis of the punch press machine.
Moreover, when the function of “positioning with optimum acceleration” is used, if the table axis movement amount exceeds a boundary value, table axis acceleration is switched (acceleration is switched by switching the speed and the acceleration and deceleration time constant) and the position gain is also switched. This poses a problem, as depicted in FIG. 12, in which table axis operation (acceleration and position gain) may be significantly changed even with a slight difference in the movement amount upon transit through the boundary value.